Self-contained hydraulic tappet



Sept. 4, 1956 c. R. KILGORE 2,761,433

SELF-CONTAINED HYDRAULIC TAPPET Filed April 4,' 1955 2 Sheets-Sheet 1aiya/@v ATTYS.

Eg. ,Z l

C. R. KILGORE SELF-CONTAINED HYDRAULIC TAPPET Sept. 4, 1956 Filed April4, 1955 2 Sheets-Sheet 2 QM @Wm/awr@ ATTYS.

United States Patent ce PatentedV Sept. 4, 19,56

SELF-CONTAINED HYDRAULIC TAPPET Charles R. Kilgore, Cleveland, Ohio,assignor to Thompson Products, Inc., Cleveland, Ohio, a corporation ofOhio Application April 4, 1955', Serial No. 498,959

7 Claims. (Cl. 12B-90) The present invention is directed to improvementsin automatic clearance regulators of the type exemplified by tappetmechanisms used in internal combustion engines.

Automatic clearance regulators are designed primarily to respond toirregularities in the mechanismv in which they are operating to take upany looseness or play in that mechanism. Such irregularities may occur,for example, by mechanical means or by thermal expansion andcontraction. For the most effective operation of valve operatingmechanisms, the system must be capable of adjusting` itself to theseirregularities in order that the valve operating mechanism may operatesmoothly and satisfactorily.

Any compensating system of the type described should not beover-compensating in that it should not over control the linkage andproduce an undesired tightness. In the case of poppet valve operatingtappets, such tightness would prevent full seating of the poppet valve.

Two factors of prime importance in the design of hydraulic typeautomatic tappets are (l) rapid response to changes in engine operatingconditions and (2) functional stability over reasonably wide speed andtemperature operating ranges. Heretofore, automatic tappets of thehydraulic type have not always been completely satisfactory, for themost part, on both counts. This inability to respond properly toexisting conditions was most pro- .improved hydraulic tappet assemblywhich can be manufactured with a minimum of expensive machiningoperations being required.

In the improved tappet assembly of the present invenltion, there isprovided a substantially cylindrical barrel closed at one end, thebarrel being substantially of unform diameter throughout its length.Slidably mounted vwithin the barrel is a plunger member with a taperedface which isreceived within a substantially cylindrical choke sleeve. Asmall annular clearance is provided between the outer periphery of theplunger and the inner periphery of the choke sleeve to permit gradualleakdown when a Vthrust load is applied to the plunger. A shoulder isprovided on the inner surface of the choke ring to limit the axialtravel of the plunger within the barrel.

Amore or less conventional seal ring is provided Within i the barrelcavity in spaced relation to the choke sleeve.

The seal ring, the choke sleeve, the lower end of the plunger, and theinner wall of the cavity thereby provide 'f two chambers for hydraulicuid. This type of structure has' the advantage of localizing the areasof high -tluid 2 1 pressure inside the choke sleeve, rather than againstthe wall of the tappet barrel as have heretofore been common.Additionally, this type of tappet structure reduces the total amount ofliquid flow accompanying tappet recovery so that the recoveryV time ismade more rapid and the required amount of hydraulic iiuid is decreased.

Other objects and features of the invention willbeapparent to thoseskilled in the a-rt from the following de.- scription of the attachedsheet of drawings which illust-rat a preferred embodiment of theinvention.

In. the drawings: 2

Figure 1 is a fragmentary view in elevation of the tappet mechanism ofthe present invention in combination with the engine valve;

Figure 2 is a cross-sectional view of one type of tappet assemblyemploying the improvements of the present invention showing the tappetin operating position;

Figure 3 is a View similar to Fig. 2l but showing the tappet in acollapsed position such as occurs upon engine shutdown with a valvebeing held open; and

Figure 4 is a greatly enlarged fragmentary view of the plunger and chokesleeve assembly.

As shown in the drawings:

In Fig. l, the tappet mechanism of' the present invention is illustratedat reference numeral 10 and includes a cylindrical hollow'barrel 11arranged to ride on the surface of a cam 12 connected to a cam shaft 13of an internal combustion engine.

The movement of the tappet mechanism 10 is arranged to open and close apoppet or engine valve 14 arranged to be seated within a valve seatprovided in an engine block 15. The valve 14 includes an elongated valvestem 14a to which a spring cap 16 is secured. A valve spring 17 has oneend bottomed against the cap 16 and its other end against a stationarypart of the engine block 15 thereby providing a spring return mechanismfor seating the valve.

The particular tappet assembly illustrated in the drawings includes acylindrical barrel 11 of substantially uniform inner diameter, thebarrel 11 Vbeing provided within a closed bottom'lla.

Disposed within the barrel 11 is a substantially cylindrical chokesleeve 20 havin-ga tapered end face 20a and an annular shoulder 20hformed thereon. The choke sleeve 204 has a at seat 20d on thefbottom ofits tapered end. vDisposed immediately above the choke sleeve 20 is aresilient seal ring 21 composed of rubber or similar material in sealingrelationship with the-inner wall of the barrel 11 and the plunger 24. Arelatively light choke sleeve spring 22 i's received between the sealring 21 and the annulus shoulder 20hon thev choke sleeve 20 to `urge thechoke ring into seated relationship against the bottom 11e.

Slidably received within the Choke sleeve 20 is a plunger 24 having aconical end face 24a disposed within the choke sleeve 20. As seen inFig. 2, the diameter of the plunger 24 is slightly less than the innerdiameter ofthe choke sleeve 20, leaving a small annular clearance 25between the 'two elements forming a leakdownpassage for vthe hydraulicuid'. A reservoir chamber 26 for the hydraulic fluid is defined by theannular space between the ychoke sleeve 20 and the wall ofthe barrel 11,theV plunger '20.' The extent of downward movement of the plunger 24within thev choke Vsleeve is identiiied at letter-A in Fig. 2. Disposedimmediately above the seal ring 21 isa slidable washer 27 axiallymovable within the barrel 11 with suicient clearance being provided topermit the plunger 24 to slide freely therethrough. The washer 27 servesto bottom the lower ends ofy a pair of springs 28 and 29. The outerspring 29 maintains a positive pressure in the reservoir 26 and theinner return spring provides the necessary operating force. The innerreturn spring 28 extends between the washer 27 and a lock ring 31 whichts into a groove formed at the upper end of the plunger 24. The outerspring 29 extends between the washer 27 and an upper washer 32. Theupward movement of the plunger 24 is limited by the engagement of thelock ring 31 with the washer 32 which in turn abuts against a snap ring33 which is received in a suitable groove in the wall of the barrel 11.p

The ycharacteristics of the innerV return spring 28 are such thatsufficiently rapid recovery for the small amount of leakdown occurringduring engine operation is accomplished without imposing a high returnforce on the valve train. n the other hand, when the tappet iscompletely collapsed during the engine shutdown period, very rapidrecovery is required to prevent excessive clatter on starting. In theVtappet of the present invention this rapid recovery is achieved byutilizing only a low volume of circulated uid.

During the operation of the engine, the tappet operates as follows. Asthe tappet moves toward the nose of the cam 12, the force of the enginevalve spring 17 moves the plunger 24 downwardly, thereby compressing theinner return spring 28 and displacing fluid from the compression chamber34 along the leak-downppassage 25. The pressure in the compressionchamber 34 acts on an area C indicated in the drawings (Figure 4), thisarea being the annular space whose width is determined by the projectionof the outer surface of the plunger 24 against the annular shoulder c ofthe choke sleeve 20. The pressure seats the choke sleeve 20 firmly onits flat seat 20a?,v the width of the seat being designated by theletter D in the drawings. The seating of the choke sleeve 20 creates apressure tight seal at the bottom of the barrel 11. The displaced fluidwhich ows from the leakdown passage '25 into the reservoir 26 causes theseal ring 21 and the lower washer 27 to move slightly upward. Thisaction further compresses the inner return spring 2S and the outerspring 29. As the engine valve 14 is seated, the force of the valvespring 17 acting on the plunger 24 reduces to zero. Immediatelythereafter, the inner return spring28 moves the plunger 24 upwardly. Atthe same time the pressure in the reservoir 26 developed by the outerspring 29 acting on an area designated at letter E in the drawingsforces the choke sleeve 20 upward, compressing the choke spring 22.Fluid ow then occurs from the reservoir 26 past the iiat seat 20d andinto the compression chamber 34. Flow continues until the plunger 24 hasmoved suticiently to remove lash in the valve train, at which time thepressures in the reservoir 26 and the compression chamber 34 becomenearly equal. The choke spring 22 then forces the choke sleeve 20downward until it seats on the tiat seat 20d on the bottom of the barrelcavity.

When the engine is stopped, some of -the tappets will be on the nose oftheir cams, holding the valves open. The force of the valve spring 17will then move the plunger 24 slowly downward until the taperedend ofthe plunger 24 stops on the shoulder 20c of the choke sleeve 20 (Figure3). When the engine is started the tappet recovers in a manner similarto that previously described.

In any hydraulic tappet, the time for tappet recovery should be as shortas possible to prevent objectionable noise. The time for tappetrecovery, in the tappets of the present invention, has been found to bemuch less than in previous types of hydraulic tappets because of thevery low volume of displaced iiuid and the comparatively large oriiicearea in the choke sleeve for uid transl fer.

With the type of tappet assembly illustrated in the drawings, the regionof high uid pressure can be confined to the interior of the choke sleeve20. Consequently, the walls of the barrel are not subjected to highiiuid pressures and therefore need not be designed to withstand suchelevated pressures.

It will be evident that various modifications can be made to thedescribed embodiment without departing from the scope of the presentinvention.

I claim as my invention:

- l. An automatic clearance regulator which comprises a housing having aside wall and a closed end, a hollow choke sleeve in the closed end ofthe housing and spaced from the side wall of the housing, seal meansengaging the side wall and confining a body of uid in said closed end ofthe housing for filling and surrounding the choke sleeve, a thrust loadtransmitting plunger having an end portion extending into said chokesleeve in leakdown clearance relationship therewith, a tappet elongatingspring compressed between said seal means and said plunger, a secondspring compressed between said seal means and said choke sleeve forurging said choke sleeve against the closed end of the housing, saidchoke sleeve providing a trapped iiuid chamber in the body of fluidconnected with the main body of iiuid surrounding the choke sleevethrough the passageway provided by the leakdown clearance relationshipbetween the plunger and choke sleeve, said elongating spring being.eiective to retract the plunger and reduce pressure in the trappediluid chamber when thrust load on the plunger is relieved whereupon uidfrom the main body will raise the choke sleeve off of the closed end ofthe housing to replenish the trapped iiuid chamber until the pressuresin the main body and trapped chamber are equalized whereupon said secondspring will reseat the choke sleeve on the closed end of the housing.

2. A lash adjuster which comprises a housing having a closed end, sealmeans slidably mounted in said housing adapted to conline a body of uidin said closed end, a plunger slidable through said seal means into saidfluid, a choke sleeve bottomed on the closed end, submerged in saidbodyof fluid and receiving the end of the plunger therein, said choke sleevebeing appreciably smaller than said housing to receive uid therearound,said plunger being slightly smaller than said choke sleeve to provide `aleakdown passageway from ra trapped fluid chamber in the choke sleeve, atappet elongating spring `operating between said seal means and saidplunger, a choke sleeve spring compressed between the seal means and thechoke sleeve urging the choke sleeve lagainst the closed end of thehousing for isolating tiuid in said trapped fluid chamber, saidelongating spring being effective to retract the plunger relative to thechoke sleeve upon release of thrust load on the plunger, and said chokesleeve spring accommodating unseating of the choke ring oi of the closedend of the housing whenever uid pressure in the isolated trapped fluidchamber is less than fluid pressure in the chamber surrounding the chokesleeve.

3. A hydraulic valve lash regulator which comprises a' barrel having aclosed end, a small diameter choke sleeve in the bottom `of the barrel,a plunger extending into said Vchoke sleeve and having leakdownclearance relationship therewith, the bottom of the barrel, the chokesleeve and the plunger providing an isolated trapped iluid chamber inthe central portion of the bottom of the barrel, an elongating springacting on the plunger to retractthe plunger from the choke sleeve, and aweaker choke sleeve spring urging the choke sleeve against the bottom ofthe barrel, fluid in said trapped uid chamber Ysupporting said plunger,and said choke sleeve spring accommodating unseating of the chokewhenever iiuid pressure in the choke sleeve is less than uid pressuresurrounding the choke ring.

4. In a tappet assembly, a cylindrical barrel having a closed end, acylindricalhollow choke sleeve disposed in said barrel in spacedrelation to said barrel thereby providing a duid reservoir therein, a.spring urging said choke sleeve against said closed end, and a plungerhaving a tapered end face received within said choke sleeve, said chokesleeve having an internal stop limiting the extent of movement of saidplunger, and said plunger having a diameter smaller than the innerdiameter of said barrel, thereby providing a space accommodatingleakdown clearance between said plunger and said choke sleeve.

5. A tappet `assembly comprising a cylindrical barrel having a closedend, a cylindrical hollow choke sleeve slidable in said barrel, a sealring about the periphery of said choke sleeve and sealingly engaging theWall of said barrel, -a spring urging said choke sleeve against saidclosed end, a plunger having a conical end received within said 'chokesleeve, said choke sleeve having an internal stop limiting the extent ofmovement of said plunger, said plunger being spaced from said chokesleeve to provide an annular clearance between said plunger and saidchoke sleeve, said closed end, said choke sleeve, and said plungerdefining a trapped fluid chamber in said barrel, said springaccommodating unseating of said choke sleeve whenever fluid pressure insaid choke sleeve is less than fluid pressure surrounding said chokesleeve.

6. A tappet assembly comprising a barrel having a closed end, acylindrical hollow choke sleeve slidable in said barrel in spacedrelation to said barrel leaving a hydraulic fluid reservoir within saidbarrel, a seal ring closing the top of said fluid reservoir, a plungerhaving a conical end received within said choke sleeve, said,

plunger being of smaller diameter than said choke sleeve thereby leavingan annular space therebetween to provide for fluid leakdowntherebetween, `and a spring urging said choke sleeve against said closedend.

7. A tappet Iassembly comprising a barrel having a closed end, -acylindrical hollow choke sleeve slidable in said barrel, a plungerhaving a conical end received within said choke sleeve, a pair ofsprings coaxially mounted about a portion of said plunger, said plungerbeing received in said choke sleeve with =a slight annular clearancetherebetween, a seal ring disposed between said choke sleeve and saidpair of springs in sealing relation to said barrel, and a return springurging said choke sleeve `against said closed end, said closed end, saidchoke sleeve and said plunger defining a trapped uid chamber in saidbarrel, said return spring accommodating unseating of said choke sleevewhenever fluid pressure in said choke sleeve is less than fluid pressuresurrounding said choke sleeve.

References Cited in the tile of this patent UNITED STATES PATENTS

